Cycle cars fascinate me. When I was about six years old I had a ride in a Morgan Barrelback that must have stuck with me.
Recently, I was given the opportunity to purchase a shaft drive Honda V-Twin
and I'm considering building a BRA style replica.

I've been all over that build thread before. Thanks guy's.
Here in the USA, 2CV's are hard to find. I'll thinking Honda V-Twin or Harley power. Preferably mated to a VW or Miata gearbox.
Also considering a Fiero or Chevette front suspension. The closest builds that I can find are the old BRA CX3 (Honda) or the JVA with a Harley. Tons of research to do. There was a Pembleton in Daytona owned to a fellow that I spoke to. He indicated that he was afraid to take it in the freeway. I believe he recently sold it. A little more Oomph for me will require a more powerful engine and perhaps a slightly longer wheelbase and front track.

I was alerted to that possibility, however, Penguin mentioned to me in my last e-mail that they were looking for an investor. We'll see.
There is a complete unassembled kit in Texas and I may have a go look soon. I believe only one of maybe two in the USA.

I would go with the Buckland, at the right price and if you can find a engine.
But the BRA3cx plans would be a good start too. I wouldn't fancy taking any small 3 wheelers on a busy freeway, some low kit cars 7ish can be scary in any British town.
Good luck

Engine & gearbox not a problem. The 1.6 Kent engine was used in many TVR's. Decked, can easily be a 1.3 if desired. I have access to many of these. If I do have to do a scratch build, the bevelbox is the only issue right now.

You could modify a Ford Sierra diff. The Buckland has a chain drive from the diff to the rear wheel. Or use the bevel drive from a shaft drive motor bike. There was a great Steampunk trike in either '100% Bike' or its sister 'Trike' a while back. That had a Virago V twin in line, like in the bike and shaft drive to the rear wheel. That setup in a BRA would look great.

You could modify a Ford Sierra diff. The Buckland has a chain drive from the diff to the rear wheel. Or use the bevel drive from a shaft drive motor bike. There was a great Steampunk trike in either '100% Bike' or its sister 'Trike' a while back. That had a Virago V twin in line, like in the bike and shaft drive to the rear wheel. That setup in a BRA would look great.

Yes, thinking of a Guzzi or Goldwing rear & diff. With the 4 speed transmission + reverse. Only need to fabricate a driveshaft and appropriate carrier bearings.